Thermal reactor for internal combustion engine fuel management system

ABSTRACT

A fuel management system for an internal combustion engine including an intake manifold is presented. The fuel management system includes a thermal reactor having an inlet port and an outlet port. The thermal reactor receives liquid fuel through the inlet port and is adapted to heat the liquid fuel and discharge fuel vapor through the outlet port. A pressure sensing device is configured to measure pressure within the intake manifold to determine engine load. A plenum is adapted to receive the fuel vapor from the outlet port and mix the fuel vapor with air, and the plenum is adapted to be connected to the intake manifold to provide the fuel vapor and air mixture to the intake manifold. A fuel metering device is operable to regulate the amount of fuel vapor provided to the plenum in response to the pressure sensing device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.09/176,011 filed Oct. 20, 1998, now U.S. Pat. No. 6,330,825, whichclaims the benefit of U.S. Provisional Patent Application No.60/063,183, filed Oct. 20, 1997. The entire disclosures of thereferenced applications are incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to internal combustion engines, and moreparticularly, to a fuel management system for an internal combustionengine fueled by a liquid hydrocarbon.

2. Description of Related Art

The operation of internal combustion engines is well known. In aninternal combustion engine, combustion of fuel takes place in a confinedspace, producing expanding gases that are used to provide mechanicalpower. The most common internal-combustion engine is the four-strokereciprocating engine used in automobiles. Here, mechanical power issupplied by a piston fitting inside a cylinder. On a downstroke of thepiston, the first stroke, fuel that has been mixed with air (by fuelinjection or using a carburetor) enters the cylinder through an intakevalve via an intake manifold. The intake manifold is a system ofpassages that conduct the fuel mixture to the intake valves. The pistonmoves up to compress the mixture at the second stroke. At ignition, thethird stroke, a spark from a spark plug ignites the mixture, forcing thepiston down. In the exhaust stroke, an exhaust valve opens to vent theburned gas as the piston moves up. A rod connects the piston to acrankshaft. The reciprocating (up and down) movements of the pistonrotate the crankshaft, which is connected by gearing to the drive wheelsof the automobile.

A diesel engine is another type of internal-combustion engine. It isgenerally heavier and more powerful than the gasoline engine and burnsdiesel fuel instead of gasoline. It differs from the gasoline engine inthat, among other things, the ignition of fuel is caused by compressionof air in its cylinders instead of by a spark. The speed and power ofthe diesel are controlled by varying the amount of fuel injected intothe cylinder.

In this disclosure, a fuel is defined as a substance that can be burnedby supplying air and a sufficient amount of heat to initiate combustion.A liquid hydrocarbon fuel, such as gasoline or diesel fuel, must beconverted to a gas before it can be ignited. This liquid to gas vaporconversion is required because the molecules of fuel must be well mixedwith the molecules of air before they can chemically react with eachother to give off heat.

However, not all of the liquid fuel must be converted to a gas beforecombustion can occur. Just enough fuel needs to be converted to a gas sothat the mixture of gas molecules and air molecules falls within thefuel's flammability limits—which refers to the minimum and maximumconcentration percentages, by weight, of fuel in air that will burn. Ifthe concentration of the gaseous fuel in air is less than the minimum orgreater than the maximum flammability limit, the fuel and air mixturewill not ignite. Known internal combustion engines and fuel deliverysystems are inefficient in converting the liquid fuel to a gaseousstate. Therefore, the fuel and air molecules cannot mix properly forcomplete combustion.

In a gasoline engine employing a standard automotive throttle body fuelinjection system, this inefficiency is due at least in part to the highvelocity of the air and fuel s mixture passing the fuel injection'sthrottle body, which may reduce the inlet temperature as low as 40° F.(4° C.). The flash point temperature—the temperature at which the fuelwill give off enough vapor to form a combustible mixture with air—forgasoline is 45° F. (7° C.). This reduction in inlet temperature reducesthe amount of heat available from the atmosphere to evaporate the fuel.Since less ambient heat is available, more energy from compressing themixture is required to evaporate the fuel.

Gasoline engines have a throttle valve to control the volume of intakeair. The amount of fuel and air that goes into the combustion chamberregulates the engine speed and, therefore, engine power. This causescontinuous changes in the atmospheric air velocity due to the pressuredifferential between the atmosphere and the intake manifold. Thesepressure variations cause the size of the particles of atomized fuel tovary throughout the engine's RPM range. As a result, there is a widevariation in fuel droplet size in the air stream. Therefore, the fueldroplets have less surface area exposed to the air for evaporation andmore heat is required to fully evaporate the fuel.

Once the fuel vapor and air mixture leaves the throttle body injectorand enters the intake manifold, the mixture velocity is so high thatsome of the fuel droplets are centrifuged out of the air stream whenthey make turns. This occurs because the fuel droplets are heavier thanair. This varies that portion of the mixture's stoichiometric fuel toair ratio, even though the overall air to fuel ratio of the mixtureflowing through the fuel injector is correct. The portion of the mixturethat contains the fuel that was centrifuged out of the main air streamreduces the amount of surface area exposed by the fuel to the air forevaporation. This increases the amount of energy required to evaporateit. Once this portion of the fuel mixture is evaporated, it burns richsince the original portion of this mixture was rich from the fuel beingcentrifuged out of the main air stream. Carbony residues that accumulatein the combustion chambers and darker areas on the piston tops indicateareas of excessive fuel richness during combustion.

Conversely, portions of the air stream that are lean, but still fallwithin the flammability limits, will burn and cause extremely hightemperatures. Auto-ignition temperature refers to the temperature atwhich a mixture of air and fuel will spontaneously ignite without openflame, spark, or a hot spot. The auto-ignition temperature of gasolineis 495° F. (275° C.). When these localized high temperature areas reachhigh enough pressure and temperature, autoignition of the end gases willresult, causing detonation, which is the uncontrolled combustion orexplosion caused by auto-ignition of the end gases that were notconsumed in the normal flame front reaction. Detonation results in thefamiliar “ping” or “spark knock” sound.

The engine's heat of compression during the compression stroke producesheat that begins to evaporate the air and fuel mixture in the cylinder.However, this compressing of the mixture increases the pressure. As aresult, the increased pressure increases the boiling point of the fuelfor evaporation. Evaporation continues slowly because theserelationships are not linear. So enough fuel evaporates, allowing it tofall within its flammability limits. Then the spark plug ignites themixture and creates a flame front. This flame front during thecombustion process has the same effect of increasing the boiling pointof the fuel so its critical temperature is never reached. Therefore, theremaining atomized fuel droplets do not evaporate before or duringcombustion. Since the droplets are not vaporized, they do not bum.

When the cylinder pressure falls due to the descent of the piston whileon the power stroke, the fuel droplets that were not evaporated earliernow evaporate due to a lower boiling point and higher cylindertemperature. These evaporated fuel droplets now burn, but they burn toolate into the crankshaft angle for producing power. Thus, less power andhigh exhaust gas temperatures result.

Direct (intake) port fuel injection has better fuel distributioncharacteristics than a throttle body fuel injection system. However,they allow very little time to evaporate fuel in the intake port.Therefore, the heat of compression must heat the air/fuel mixture forevaporation before combustion can occur. This system has the sameinherent inefficiencies regarding the engine's heat of compression,which increases the boiling point of the fuel. Therefore, as thecylinder pressure rises, the critical temperature is never reached. Theremaining fuel droplets do not burn in time to produce power. Thus, lesspower and high exhaust gas temperatures still result.

The heat of combustion (the temperature in the cylinder due tocombustion) for gasoline is 840° F. (449° C.) plus or minus 40° F. (4°C.) above ambient. Conventional automotive exhaust gas temperatures are1,400 to 1,500° F. (760 to 815° C.). This temperature difference (heatenergy) between the exhaust gas temperature and the heat of combustionis totally wasted as excessive exhaust gas temperature. Even theengine's cooling system must be enlarged to dissipate the higher exhaustgas temperatures due to the increased temperature differential aroundthe exhaust side of the combustion chambers and exhaust ports. Thiswasted heat energy is dissipated to the atmosphere through the vehicle'sradiator, and an equal amount of wasted heat energy is dissipatedthrough the vehicle's exhaust pipes as excessively high exhaust gastemperatures.

The remaining fuel that did not chemically react in the combustionchamber or in the exhaust manifold then enters a 2,000° F. (1,093° C.)catalytic converter for combustion. The unburned fuel that escapes thecatalytic converter enters the atmosphere as hydrocarbon andcarbon-monoxide pollutants. Moreover, currently produced catalyticconverters are only effective when the engine is at operatingtemperature, so it has no effect on cold start emission levels.

Similar shortcomings exist with known diesel engines. In diesel engineswith indirect fuel injection (precombustion chamber), the engine's heatof compression during the compression stroke produces heat that beginsto evaporate the air and fuel mixture in the cylinder. However, thiscompressing of the mixture increases the pressure. As a result, theincreased pressure increases the boiling point of the fuel forevaporation. Evaporation continues slowly because these relationshipsare not linear, and just enough of the aromatics in the diesel fuelevaporate allowing it to fall within its flammability limits. The flashpoint temperature of the aromatics is low enough for the air and fuelmixture to auto-ignite, which results in a flame front. This flame frontignites more of the fuel mixture during the combustion process; however,it has the same effect of increasing the boiling point of the fuel soits critical temperature is never reached. Therefore, the remainingliquid fuel droplets do not evaporate before or during combustion.

Diesel engines with direct-injection (DI) have even greater fuelvaporization problems. In a diesel engine with DI high turbulencecombustion chambers, the fuel spray pattern elongates in response to airflow. The smaller fuel droplets concentrate on the leading (lower) edgeof the spray pattern while the larger and heavier droplets remainclustered about the core.

Ignition begins as a series of small bursts at the interface between thefuel spray and cylinder air, where there is surplus of oxygen. Thebursts combine into flame fronts that progressively move into thefuel-soaked core of the pattern. Every normal combustion event in adiesel engine begins under oxygen-rich conditions and concludes underoxygen-lean conditions. This variability in fuel/air ratios is a specialburden of the diesel engine. In addition, diesel engines operate under afairly wide range of loads and speeds. Air turbulence, duration of theexpansion stroke (power), and cylinder temperature vary with theoperating mode.

Hydrocarbons survive their passage through the cylinder when the mixtureis either too lean or too rich to burn. Excessively lean mixtures arecaused by fuel droplets that break free of spray plume and diffusethroughout the combustion chamber. The resulting fuel mixture does notsupport combustion, and the raw fuel exists through the exhaust. Thisphenomenon often occurs under light loads and at low engine speeds,which causes high hydrocarbon emission spikes during idle. Hydrocarbonemissions are also generated when the flame is quenched by too rapidinfusion of air or by contact with the relatively cool cylinder walls.

Particulate Matter (PM) in high concentrations that accompany dieselacceleration and cold starts can be seen as black smoke. The hydrocarboncomponent of PM, referred to as soluble organic fraction (SOF), consistsof combustion by-products, lube oil and unburned fuel. Soot, the SOFcarrier, forms in the oxygen-poor (rich fuel mixture) region on thetrailing edge of the fuel plume. Oxides of nitrogen (NOx) are created inthe high-temperature, oxygen-rich combustion (fuel-lean mixture) thatoccurs on the leading edge of the spray plume. Most soot forms early inthe combustion process when fuel accumulates during the ignition lagperiod, then burns at extremely high temperatures to form NOx.

When the cylinder pressure falls due to the descent of the piston whileon the power stroke, the fuel droplets that were not evaporated earliernow evaporate due to a lower boiling point and higher cylindertemperature. These evaporated fuel droplets now burn, but they burn toolate into the crankshaft angle for producing power. Thus, less power,high emission levels, and high exhaust gas temperatures result.

The heat of combustion for diesel fuel is 500 to 550° F. (260 to 288°C.) above ambient. Convention diesel exhaust gas temperatures are 1,100to 1,300° F. (593 to 704° C.). As with a gasoline engine, thistemperature difference (heat energy) between the diesel exhaust gastemperature and the heat of combustion is totally wasted as excessiveexhaust gas temperature. Thus, the engine's cooling system must beenlarged to dissipate the higher exhaust gas temperatures due to theincreased temperature differential around the exhaust side of thecombustion chambers and exhaust ports. This wasted heat energy isdissipated to the atmosphere through the vehicle's radiator, and anequal amount of wasted heat energy is dissipated through the vehicle'sexhaust pipes as excessively high exhaust gas temperatures.

The present invention addresses some of the above mentioned, and other,shortcomings associated with the prior art.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a fuel management system for aninternal combustion engine is presented. The internal combustion engineincludes, among other things, an intake manifold, and the fuelmanagement system includes a thermal reactor having an inlet port and anoutlet port. The thermal reactor receives liquid fuel through the inletport, and is adapted to heat the liquid fuel and discharge fuel vaporthrough the outlet port. A pressure sensing device is configured tomeasure pressure within the intake manifold to determine engine load,and a plenum is adapted to receive the fuel vapor from the outlet portand mix the fuel vapor with air. The plenum is adapted to be connectedto the intake manifold to provide the fuel vapor and air mixture to theintake manifold. A fuel metering device is operable to regulate theamount of fuel vapor provided to the plenum in response to the pressuresensing device.

In another aspect of the invention, a thermal reactor for converting aliquid hydrocarbon fuel to a fuel vapor includes a cylinder defining anaxial bore therethrough. The cylinder further defines an inlet portadapted to receive the liquid hydrocarbon fuel, and an outlet portadapted to discharge the fuel vapor. At least one heating element isconnected to the cylinder and is arranged to heat the liquid hydrocarbonfuel to convert the liquid fuel to the fuel vapor.

In yet another aspect of the present invention, a system for preventingcylinder over scavenging during the overlap period of a camshaft in aninternal combustion engine is provided. The engine includes an exhaustmanifold and an exhaust pipe coupled thereto. The system includes apressure sensor to measure back pressure of exhaust gas from the engineand a control valve coupled to the exhaust pipe. The control valve isresponsive to the pressure sensor to restrict the exhaust gases andapply back pressure on the engine.

In a still further aspect, a method of dynamically mapping operatingparameters of an engine is provided. The method includes configuring aplurality of measurement devices to indicate a plurality of engineparameters, operating the engine, recording the outputs of themeasurement devices while the engine is operating, and playing back therecorded outputs at predetermined time intervals. In a particularembodiment, the recording of the outputs comprises video taping theoutputs of the measurement devices.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thedrawings in which:

FIG. 1 is a block diagram illustrating a fuel management system inaccordance with an embodiment of the present invention;

FIG. 2 is a block diagram illustrating a fuel management system inaccordance with an alternative embodiment of the present invention;

FIG. 3 is a block diagram illustrating a fuel management system inaccordance with another alternative embodiment of the present invention;

FIG. 4 is a side view of an embodiment of a thermal reactor inaccordance with the present invention;

FIG. 5 is a front perspective view of a cylinder suitable for a thermalreactor such as the embodiment illustrated in FIG. 4;

FIG. 6 is a perspective view of a first end plate for a thermal reactorsuch as the embodiment illustrated in FIG. 4;

FIG. 7 is a perspective view of a second end plate for a thermal reactorsuch as the embodiment illustrated in FIG. 4;

FIG. 8 is a perspective view of a cylinder adapted for an alternativeembodiment of a thermal reactor in accordance with the presentinvention;

FIG. 9 is a front perspective view of a fuel metering device inaccordance with an embodiment of the present invention;

FIG. 10 is a top perspective view of the fuel metering device shown inFIG. 9;

FIG. 11 is a side perspective view of the fuel metering device shown inFIG. 9;

FIG. 12 is a block diagram illustrating a fuel management system inaccordance with yet another alternative embodiment of the presentinvention;

FIG. 13 is a perspective view of a plenum in accordance with anembodiment of the present invention;

FIG. 14 is a block diagram illustrating an exhaust control system inaccordance with an embodiment of the present invention;

FIG. 15 is a perspective view of an exhaust system thermal reactor inaccordance with the present invention; and

FIG. 16 illustrates a glow plug system in accordance with an embodimentof the present invention;

FIG. 17 is a flow diagram illustrating a mapping process in accordancewith an embodiment of the present invention.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

FIG. 1 is a block diagram illustrating a fuel management system 100 inaccordance with one embodiment of the present invention. Specificembodiments of the present invention are configured for use as an add-onsystem for an original equipment manufacture's (OEM) engine. The fuelmanagement system 100 is adapted for use with an internal combustionengine 110 using a liquid hydrocarbon fuel 112, such as gasoline, dieselfuel, kerosene, alcohols, etc., which is typically contained in a fueltank. Among other things, the engine 112 includes an intake manifold 114for conducting an air/fuel mixture to the intake valves (not shown) ofthe engine 112.

The exemplary fuel management system 100 includes a thermal reactor 120having an inlet port 122 and an outlet port 124. The thermal reactor 120receives liquid fuel 112, typically from a vehicle's fuel tank, throughthe inlet port 122. The thermal reactor 120 heats the liquid fuel 112 toconvert it to fuel vapor, which is then discharged through the outletport 124. A plenum 126 receives the fuel vapor and thoroughly mixes itwith air. The fuel vapor and air mixture then flows from the plenum 126to the intake manifold 114 to provide the fuel vapor and air mixture tothe intake manifold. A pressure sensing device 128 is configured tomeasure pressure within the intake manifold 114 to determine engineload, and a fuel metering device 130 is operable to regulate the amountof fuel vapor provided to the plenum 126 in response to the pressuresensing device 128, thus providing the leanest possible air to fuelvapor ratio for the engine 112 load condition. In certain embodimentsadapted for use with a turbocharged engine, such as a turbochargeddiesel engine, the engine's native turbocharger may provide the functionof the plenum 126. Hence, the plenum 126 would not be necessary in suchan implementation, and the fuel vapor from the thermal reactor 120 wouldbe provided directly to the turbocharger.

The fuel metering device 130 may be situated in various positionsrelative to the thermal reactor 120 in accordance with variousembodiments of the invention. In a particular embodiment, such as thesystem 101 illustrated in FIG. 2, the fuel metering device 130 isconnected to the outlet port 124 of the thermal reactor 120, such thatthe fuel vapor passes from the thermal reactor 120 outlet port 124,through the fuel metering device 130, to the plenum 126. In anotheralternative embodiment shown in FIG. 3, the fuel metering device iscoupled to the inlet port 122 of the thermal reactor 120, such that theliquid fuel 112 passes through the fuel metering device 130 to thethermal reactor inlet 122.

Turning now to FIG. 4 and FIG. 5, an exemplary thermal reactor 120 inaccordance with a particular embodiment of the invention is illustrated.The thermal reactor 120 functions to heat liquid fuel to convert it to afuel vapor, and further, it serves as a surge tank of fuel vapor to meetengine demands while liquid fuel is being processed. The thermal reactor120 comprises a cylinder 140 defining an axial bore 142 therethrough.The cylinder 140 is adapted to receive the liquid fuel 112 from theinlet port 122 and discharge the fuel vapor through the outlet port 124.In the particular embodiment illustrated in FIG. 4 and FIG. 5, a firstend plate 144 that is connected to a first end 145 of the cylinder 140defines the inlet port 122, and a side wall 146 of the cylinder 140defines the outlet port 124. At least one heating element 148 isprovided to heat the liquid fuel and thus, to convert the liquid fuel tothe fuel vapor.

The thermal reactor 120 shown in FIG. 4 and FIG. 5 includes a pluralityof heating elements 148 disposed in the cylinder 140, with the heatingelements 148 arranged such that the liquid fluid contacts the heatingelements 148. The side wall 146 of the cylinder 140 has a plurality ofapertures 150 extending therethrough, with each of the apertures 150having one of the heating elements 148 extending therethrough, so thateach heating element 148 projects into the cylinder 140 (only twoheating elements 148 are shown extending through the apertures 150 inFIG. 5 to simplify the illustration). In certain embodiments, each ofthe heating elements 148 is positioned generally perpendicular to theaxis of the cylinder 140, and each of the apertures 150 has acorresponding aperture 150 located about 90 degrees therefrom, asillustrated in FIG. 5. More specifically, the apertures 150 are arrangedin two columns, with each column being generally parallel to the axis ofthe cylinder 140 and positioned about 90 degrees apart.

In one specific embodiment of the thermal reactor 120A, the cylinder 140is about 12.125 inches (30.80 cm) long, with a diameter of about 4.0inches (10.2 cm). Each of the columns 151, 152 of apertures 150 includes12 apertures, for total of 24 apertures 150 extending through thecylinder 140. Each aperture 150 is 0.375 inches (0.95 cm) in diameterand is threaded. The apertures 150 are positioned such that the centerof the first aperture 150 of the first column 151 is 1.3125 inches (3.33cm) from the first end 145 of the cylinder 140, and the first aperture150 of the second column 152 is 0.9375 inches (2.38 cm) from the firstend 145 of the cylinder 140. The remaining apertures 150 are spaced0.975 inches (2.48 cm) on center. The outlet port 124 comprises athreaded 0.5 inch (1.27 cm) opening. Vulcan 250 watt cartridge heatersare suitable heating elements 148. In one embodiment, 12 volts DC isused to power the heating elements 148.

FIG. 6 and FIG. 7 illustrate embodiments of first and second end plates144, 160, respectively, adapted for use with the cylinder 140illustrated in FIG. 5. Referring to FIG. 6, the first end plate 144defines an opening 162 therethrough to accommodate the inlet port 122.The first end plate 144 further defines four bolt holes 164 extendingtherethrough about the periphery of the first end plate 144, with fourgenerally cylindrical spacers 166 associated with each of the bolt holes164. Four coupling feet 170 corresponding to the bolt holes 164 areconnected to the cylinder 140 (shown in FIG. 4). Four bolts 168 extendthrough the bolt holes 164, the spacers 166, and the coupling feet 170,and washers and nuts (not shown) are placed about the bolts 168 to affixthe first end plate 144 to the cylinder 140 in a sealing relationship.

In one embodiment, the first end plate 144 is 0.375 inches (0.952 cm)thick with a diameter of 6 inches (15.24 cm). The inlet port opening 162comprises a threaded 0.125 inch (0.318 cm) opening, and the bolt holes164 each comprise threaded 0.250 inch (0.635 cm) openings. The spacers166 are each 1.250 inches (3.175 cm) long, and the bolts 168 are each2.50 inches (6.35 cm) long with 0.25 inch (0.635 cm) washers and nuts.The first end plate 144 further defines a sealing lip 172, which in oneembodiment, is 3.997 inches (10.152 cm) in diameter and extends 0.125inches (0.318 cm) above the surface of the first end plate 144.

Turning now to FIG. 7, the second end plate 160 includes bolt holes 164,spacers 166 and bolts 168 to connect the second end plate 160 to thecylinder 140 via the coupling feet 170 in a manner similar to the firstend plate 144 as disclosed in conjunction with FIG. 6. In a particularembodiment, the second end plate 160 further defines openings throughwhich a K-type thermocouple 180, a pressure sensor 182, and two hightemperature thermal switches 184 extend. Suitable devices include amodel K thermocouple, a Hobbs 76062 NC pressure sensor, and VulcanCal-stat 1c1c5 high temperature thermal switches. These componentsfunction as part of a feedback system to maintain a preset pressure andtemperature in the thermal reactor 120. One high temperature thermalswitch 184 is used for over-temperature protection of the thermalreactor, while the other switch 184 is used for starter interrupt untilthe thermal reactor 120 has reached its operating temperature.

In some implementations of the fuel management system 100, the heatingelements 148 are operated such that the temperature of the specificheating elements 148 varies to achieve the desired conversion of theliquid fuel to a fuel vapor. Varying the temperature of the heatingelements 148 by approximately 200° F. (93° C.) from one end of thethermal reactor 120 to the other creates a vortex that spreads theliquid fuel across inside surface of the cylinder, providing maximumsurface area for heating the liquid fuel to convert it to a fuel vapor.In a particular embodiment, the thermal reactor 120 includes a brass (orother heat-conducting material) matrix within the cylinder 140 that isheated by the heating elements 148. The vortex created by varying thetemperature of the heating elements 148 causes the liquid fuel to spreadabout the brass matrix to increase the surface area for heating theliquid fuel. The brass matrix also helps insure that liquid fuel ismaintained in the thermal reactor 120 until it is completely vaporized.

FIG. 8 illustrates an alternate configuration for heating the liquidfuel 112 to transform it to fuel vapor in accordance with anotherembodiment of the present invention. At least one fuel bar 190 isconnected to the side wall 146 of the cylinder 140. Two fuel bars 190are used in the particular embodiment illustrated in FIG. 8. Each fuelbar 190 defines at least one fuel well (not shown) therein. The sidewall 146 of the cylinder 140 defines a plurality of openings thatcorrespond to openings in each fuel well, such that, when the fuel bars190 are coupled to the cylinder 140 as shown in FIG. 8, the fuel wellsare in fluid communication with the cylinder 140. Each fuel well definesan inlet port 122 that is adapted to be connected to the fuel sourcesuch that the liquid fuel 112 flows into the fuel well. In oneembodiment, each fuel well includes a fuel fitting situated toperpendicularly intersect the fuel well. Each fuel well has a heatingelement 148 associated therewith disposed within the fuel bar 190, so asto heat the liquid fuel 112 within the fuel well to convert the liquidfuel 112 to the fuel vapor. The fuel vapor then enters the cylinder 140and flows out of the cylinder 140 through the outlet port 124.

In one embodiment, each fuel bar 190 is 16 inches (40.64 cm) long, 4inches (10.16 cm) high, and 1 inch (2.54 cm) wide. Each fuel bar 190defines 24 fuel wells, which each comprise a bore 192 extending throughthe fuel bar 190. One end of each bore 192 cooperates with acorresponding opening in the side wall 146 of the cylinder 140, and theother end of the bore 192 has a heating cartridge (not shown) insertedtherein. Suitable heating cartridges include Bosch 80025, which areheated to a temperature of about 1,450° F. to 1,472° F. (788° C. to 800°C.). In a particular embodiment, the fuel wells are lined with brassinserts to improve the conduction of heat through the bores 192. Thefluid inlet ports 122 each comprise a 0.3125 inch (0.7938 cm) hole 194extending 0.900 inch (2.286 cm) into the side of the fuel bar 190generally perpendicular to the bores 192 for the fuel wells. Each of theholes 194 for the inlet ports 122 may be provided with a filter tofilter the liquid fuel 112 entering the fuel bar 190.

The thermal reactor 120 of the fuel management system of the presentinvention addresses problems associated with known internal combustionengines using liquid hydrocarbon fuels. The thermal reactor 120 allows acomplete phase change from liquid gasoline to a gaseous state withoutthe associated restriction of volume. All heavy ends of the liquid fuelare vaporized so it does not drip. The thermal reactor 120 converts theliquid fuel to a vapor which puts enough random kinetic energy into thefuel so critical temperature can be reached in the cylinder and the heatof condensation does not return the fuel to a liquid state.

In the particular fuel management system 101 illustrated in FIG. 2, thehot fuel vapor exits the outlet 124 of the thermal reactor 120 andenters the fuel metering device 130. In one embodiment, the fuel vaporexits the thermal reactor at about 650° F. (343° C.). The purpose of thefuel metering device 130 is to operate the engine 110 as fuel lean aspossible for the engine's particular load condition. To this end, a fuelmetering device 130 in accordance with one embodiment of the inventionis operable between first and second stages in response to the pressuresensing device 128 to regulate the air to fuel vapor ratio based on theload condition of the engine 110. The first stage provides fuel vaporfrom the thermal reactor 120 to the plenum 126 at a first rate toachieve a first predetermined air to fuel vapor ratio, and the secondstage provides fuel vapor from the thermal reactor 120 to the plenum 126at a second rate to achieve a second predetermined air to fuel vaporratio.

In a specific embodiment, the first stage is maximum lean, and thesecond stage increases the fuel to air vapor ratio for acceleration.Once the acceleration requirement is met, the second stage of the fuelmetering device 130 returns the fuel vapor flow to the best leanrequirement for the engine load. In other words, the first stage iseconomy cruise, and the second stage is for power.

An exemplary fuel metering device 130 is illustrated in FIG. 9, FIG. 10and FIG. 11. The fuel metering device 130 is operated by two rotaryvacuum motors 210, 211. In other embodiments, other drive mechanisms areused, such as positive pressure. FIG. 12 is a block diagram illustratinga fuel management system 103 in accordance with an alternativeembodiment of the invention, further including an intake air venturi 220coupled to the intake manifold 114 to provide a vacuum source foroperating the vacuum motors 210, 211. A controller 222 receives anoutput signal from the pressure sensing device 128 and in responsethereto, switches the fuel metering device 130 between the first andsecond stages. In the embodiment illustrated, the controller 222provides a vacuum signal from the venturi 220 to drive the vacuum motors210, 211.

In one embodiment, the controller 222 comprises a programmable logicarray, such as a model Bimbo 1224DC010DC, which is programmed using ROMMAX 4G software. The controller 222 operates the fuel metering device130 in response to engine load conditions as determined by the pressuresensing device 128, which may comprise a Sierra model 600 air flowmeter. Other system parameters used for controlling the fuel meteringdevice 130 may include, but are not limited to, mass air flow, throttleposition, engine speed, and liquid fuel temperature.

Referring to FIG. 11, each of the vacuum motors 210, 211 includes acylinder 230 and a drive shaft 232 having rack gear 234 thereon. In oneembodiment, the rack gear 234 include 32 teeth per inch (12.6 teeth percm). The rack gear 234 cooperates with drive gears 236 extending from ametering block 238. Each drive gear 236 is coupled to a respectiverotary valve (not shown) disposed within the fuel metering device 130.The fuel metering device 130 further includes a fuel vapor inlet 240 anda fuel vapor outlet 242.

In the fuel management system 103 illustrated in FIG. 12, liquid fuelenters the thermal reactor 120 and is completely converted to a fuelvapor, which exits the thermal reactor 120 and enters the fuel meteringdevice 130. The controller compares the pressure within the intakemanifold 114 as determined by the pressure sensor 128 and the vacuumsignal from the intake air venturi 220, and sends a vacuum signal to thevacuum motors 210, 211 to operate the fuel metering device 130 so as toprovide the leanest possible air to fuel vapor ratio for the engine's112 load requirement.

More specifically, the fuel metering device 130 utilizes two stages. Thefirst stage of the fuel metering device 130 is used for economy cruise.In this mode, the engine 110 will not produce maximum horsepower becausemore air and less fuel is being introduced thus providing a very leanair/fuel mixure. The second stage increases the air/fuel vapor ratio upto stoichiometeric thus providing the maximum air/fuel ratio foracceleration and power. In the vacuum system, two vacuum actuatedBarksdale model d1h-h18ss switches are used to measure intake manifold114 vacuum (engine load) and venturi 220 vacuum (engine RPM). When thethrottle position changes, a vacuum differential switch, such as aBarksdale Vacuum Differential Switch model 0-30 hg, senses thecorresponding change in intake manifold vacuum. This switch then sends acorresponding vacuum signal to the vacuum motor associated with thefirst stage, for example, the vacuum motor 210, if the vehicle iscruising, or to the vacuum motor 211 associated with the second stage ifthe vehicle is accelerating.

Turning now to FIG. 13, an exemplary embodiment of the plenum 126 isillustrated. The plenum provides more time for the air and fuel vapor tomix for enhanced combustion. It also provides additional mass to dampenthe reflecting waves that bounce off of the engine's intake valves whenthey close, thereby preventing intake air from backing out of theengines intake manifold 114. The plenum 130 illustrated in FIG. 13includes a generally cylindrical central portion 250, an inlet end 252through which the air and fuel vapor is received, and an outlet end 252,which is adapted to be connected to the intake manifold 114. The centralportion 250 may suitably be fabricated out of brass 360, stainless steel420, or a ceramic material. In a particular embodiment, glass is usedfor the central portion 250 to allow visual observation of the air andfuel vapor mixture flowing through the plenum. In one embodiment, thecylindrical central portion 250 is about 10 inches (25.4 cm) long with adiameter of 4 inches (10.16 cm), though these dimensions will varydependent on the engine's intake velocity range.

The particular fuel management system of the present invention that isillustrated in FIG. 12 includes an intake air velocity control valve 260coupled between the fuel metering device 130 and the plenum 126.Referring to the plenum illustrated in FIG. 13, the intake air velocitycontrol valve 260 is coupled to the inlet end 252 of the plenum 126. Theintake air velocity control valve 260 is operated, for example, by avacuum motor 261, and includes an air inlet 262 at a first end, and asecond end 264 that is coupled to the inlet end 252 of the plenum. Theintake air velocity control valve 260 defines an air flow path (notshown) between the air inlet 262 and the second end 264, and a variableair flow restrictor (not shown) positioned within the air flow path. Inone embodiment, a butterfly valve is used, and in another embodiment, arotary valve is used.

In the fuel management system 103 illustrated in FIG. 12, the hot fuelvapor leaves the fuel metering device 130 and flows through the intakeair velocity control valve 260. The intake air velocity control valve260 increases the engine's volumetric efficiency at low speeds byincreasing the speed of the air and fuel vapor mixture, allowing moreair to enter the engine's 110 combustion chamber while the intake valveis open. Further, a vane in the throat of the intake air velocitycontrol valve 260 causes the intake air to swirl, resulting in a vortexthat thoroughly mixes the air and fuel vapor molecules as they enter theplenum 126. The intake air velocity control valve 260 is operated tomaintain a predetermined vacuum (for example, 10 in/h20 vacuum) on theplenum 126. As discussed above, the plenum 126 provides additional timefor the air and fuel vapor to mix, allowing the mixture to completelycombust.

From the engine's intake manifold 114, the air and fuel vapor mixtureenters the engine's 110 combustion chamber where it burns and exits theexhaust system at high velocity, common with all internal combustionengines. The high exhaust velocity creates a vacuum in the exhaustpipes, which is used to pull fresh air into the engine's cylindersduring the camshaft overlap period of the intake stroke. This improvesvolumetric efficiency and maximum engine torque. This pulse scavengingof the cylinders is typically tuned for the engine's RPM associated withmaximum torque. However, at any engine speed below maximum torque, theengine is over scavenged, resulting in a lower torque curve at lowerengine speeds. This is an engineering compromise associated with knowninternal combustion engines.

FIG. 14 illustrates an exhaust control system 300 in accordance with anembodiment of the fuel management system of the present invention. Theexhaust control system 300 prevents or reduces cylinder over scavengingduring the overlap period of the camshaft in the internal combustionengine 110. The exhaust gas flows from an exhaust manifold 310, throughan exhaust pipe 312 to a muffler 312. An exhaust velocity control valve320 is connected between the exhaust manifold 310 and the muffler 312 torestrict the exhaust gas velocity just to the point that nominal backpressure prevents fresh air from entering the exhaust manifold310—typically at low speed. In one embodiment, a rotary valve is usedfor the exhaust velocity control valve 320. A vacuum motor 322, forexample, may be used to operate the exhaust velocity control valve 320in response to a pressure sensor 324 that is adapted to determine theexhaust gas back pressure. In the illustrated embodiment, the pressuresensor 324 is coupled to the exhaust manifold. The vacuum motor 322 mayoperate the exhaust velocity control valve 320 in response toadditional, or other, desired engine parameters, such as engine load (asdetermined by the pressure sensor 128) and RPM requirements.

In another specific embodiment of the fuel management system, an exhaustsystem thermal reactor 340 is coupled to the exhaust manifold 310 so asto use spent exhaust gas energy for partial heating of the liquidhydrocarbon fuel. In a system employing the exhaust system thermalreactor 340, the exhaust velocity control valve 320 further functions toinsure that the exhaust system thermal reactor 340 is filled withexhaust gases throughout the range of engine conditions. The exhaustsystem thermal reactor 340, however, only provides heating of the liquidfuel 112 when the engine 110 is at operating temperature. Thus, theexhaust system thermal reactor 340 is used for partial heating of theliquid fuel; the thermal reactor 120 controls the final fuel vaporoutlet temperature and provides cold start capability.

FIG. 15 illustrates an exemplary embodiment of an exhaust system thermalreactor 340. The exhaust system thermal reactor 340 comprises a roundcylinder 342 that is packed with a conductive matrix (not shown). Theexhaust pipe 312 passes through the center of the cylinder 342 to heatthe matrix. A fuel dispersion tube 344 is positioned above the exhaustpipe 312 to spray liquid fuel through the matrix and over the exhaustpipe 312. The fuel dispersion tube 344 defines a plurality of holes fordistributing the liquid fuel. In a particular embodiment, the fueldispersion tube defines 56 holes, each having a diameter of 0.015 inch(0.381 mm). The holes are arranged with an included angle of 90° drilledlongitudinally on the tube to distribute the liquid fuel evenly over theexhaust pipe 312 and through the matrix, thus providing the maximumsurface area for heating the fuel.

Some internal combustion engines, such as a gasoline engine, use a sparkignition system. Diesel engines use an auto-ignition system. When thefuel management system, and particularly the thermal reactor of thepresent invention, is used in conjunction with a diesel engine,auto-ignition of the air and fuel vapor mixture is no longer possible.Therefore, another form of ignition is necessary. In accordance withaspects of the invention, a combustion chamber glow plug system isprovided. The glow plug system is illustrated in FIG. 16 The glow plugsystem 370 includes a plurality of adapters 372 for replacing dieselfuel injector nozzles with diesel engine glow plugs 374, such as Delco11G glow plugs, such that at least a portion of the glug (i.e., the glowplug tip) extends into the engine's combustion chamber or pre-combustionchamber. This provides a source of fuel mixture ignition, instead of theauto-ignition method typically used with diesel engines.

In one embodiment of the glow plug system 370, the tip temperature ofthe glow plugs 372 is varied from 1,200° F. to 1,550° F. (649° C. to843° C.). A control module 376 controls the tip temperature in responseto predetermined engine parameters, such as engine load and RPM, thusproviding a mechanism for advancing or retarding the engine's ignitiontiming based on the desired engine parameter. An example of a suitablecontrol module 376 is a Red Lion PAXT0000 that includes an ECG2764EPROM. The system is responsive to the intake manifold pressure sensor128 (engine load) and a tach sensor (engine RPM). When the engine loadincreases, manifold vacuum decreases which lowers the temperature of theglow plugs 372. At idle speed, the temperature of the glow plugs 372 isabout 1,550° F. (843° C.), and the temperature decreases to about 1,200°F. (649° C.) under full load. When the engine RPM exceeds maximumtorque, the control module 376 is programmed to increase the glow plug372 temperature to compensate for the engine's loss in volumetricefficiency. In a specific embodiment, the temperature of the glow plugs372 is increased by the same percent as the volumetric efficiency loss.

In accordance with another aspect of the present invention, a novelprocess for dynamically mapping operating parameters of the engine 112is provided. Calibrating or otherwise adjusting the multiple componentsof an engine system, such as the fuel management system of the presentinvention, requires simultaneously studying and analyzing a myriad ofengine operating parameters. To further complicate the analysis, theengine parameters are constantly changing depending on the engine load,speed, etc.

FIG. 17 is a flow diagram illustrating a mapping process in accordancewith the present invention. In block 400, a plurality of measurementdevices are configured to indicate a plurality of engine parameters tobe analyzed. In block 402, the engine is operated as desired. Theoutputs of the measurement devices are then recorded while the engine isoperating in block 404. After the engine has been operated for thedesired time, and/or through the desired operational criteria, therecorded outputs are played back at predetermined time intervals inblock 406. This allows the technician to view the recorded parameters atany given time as desired to analyze various parameters occurringsimultaneously, even if a given parameter occurs for only a short timeperiod. For example, the outputs of the measurement devices may berecorded on a digital recording device, such as a personal computer harddisk, or the outputs may be video taped.

A Panasonic Pro 456AG video camera is a suitable video tape recorder. Inspecific implementations, the recorded parameters include fuel vaporpressure, intake manifold pressure, temperature, relative humidity,altitude, engine oil temperature, battery voltage, liquid fuel pressure,engine coolant temperature, etc. Further, a performance computer, suchas a Veri-Com VC2000 performance computer, may be used to measure anddisplay other parameters in real time, which may then be recorded forsubsequent play back in accordance with the method of the presentinvention. Such parameters include G-force, time, speed, distance,horsepower, RPM, torque and gear ratio. Further, these parameters aremeasured at 0.01 second intervals.

Thus, the present invention provides a system that may be used inconjunction with conventional internal combustion engines using liquidhydrocarbon fuels, such as gasoline, diesel, methanol, ethanol, etc. Thefuel management system permits complete combustion of the air and fuelvapor mixture, thereby significantly reducing exhaust emission levelsand improving fuel economy. Moreover, the system disclosed hereinfunctions to reduce cold start emissions to levels comparable to naturalgas or propane fueled vehicles.

It will be appreciated by those of ordinary skill in the art having thebenefit of this disclosure that the embodiment illustrated above iscapable of numerous variations without departing from the scope andspirit of the invention. It is fully intended that the invention forwhich a patent is sought encompasses within its scope all suchvariations without being limited to the specific embodiment disclosedabove. Accordingly, the exclusive rights sought to be patented are asdescribed in the claims below.

What is claimed is:
 1. A thermal reactor for converting a liquidhydrocarbon fuel to a fuel vapor, comprising: a cylinder defining anaxial bore therethrough, the cylinder defining an inlet port adapted toreceive the liquid hydrocarbon fuel, the cylinder defining an outletport adapted to discharge the fuel vapor; and a plurality or heatingelements disposed in the cylinder, the heating elements arranged suchthat the liquid hydrocarbon fuel contacts the heating elements to heatthe liquid hydrocarbon fuel to convert the liquid fuel to the fuelvapor.
 2. The thermal reactor of claim 1, wherein the cylinder defines aside wall having a plurality of apertures therethrough, each of theapertures having one of the heating elements extending therethrough suchthat each heating element projects into the cylinder.
 3. The thermalreactor of claim 2, wherein each of the heating elements is generallyperpendicular to the axis of the cylinder.
 4. The thermal reactor ofclaim 2, wherein each of the apertures has a corresponding aperturelocated about 90 degrees therefrom.
 5. The thermal reactor of claim 2,wherein the apertures are arranged in two columns, each column beinggenerally parallel to the axis of the cylinder, the columns beingpositioned about 90 degrees apart.
 6. A thermal reactor for converting aliquid hydrocarbon fuel to a fuel vapor, comprising: a cylinder definingan axial bore therethrough, the cylinder defining an inlet port adaptedto receive the liquid hydrocarbon fuel, the cylinder defining an outletport adapted to discharge the fuel vapor; and at least one fuel barconnected to a side wall of the cylinder, the fuel bar defining at leastone fuel well in fluid communication with the axial bore of thecylinder, the fuel well defining the inlet port such that the liquidfuel flows into the fuel well; wherein at least one heating element isdisposed within the fuel bar so as to heat the liquid fuel within thefuel well to convert the liquid fuel to the fuel vapor.
 7. A thermalreactor for converting a liquid hydrocarbon fuel to a fuel vapor,comprising: a cylinder defining an axial bore therethrough, the cylinderdefining an inlet port adapted to receive the liquid hydrocarbon fuel,the cylinder defining an outlet port adapted to discharge the fuelvapor; and means connected to the cylinder for heating the liquidhydrocarbon fuel to convert the liquid fuel to the fuel vapor.